THERE’S a joke to be had here somewhere. There must be. Something about dogs or bites or both. Maybe a reference to Celtic getting their collars felt. Or Aberdeen’s muzzles coming off.

There has to be a gag in there surely but now hardly feels like the time for glib cliches or lighthearted wordplay. No, suddenly things just got far too serious for all that.

Certainly, as Celtic made their way back to Glasgow from the North East late last night there was absolutely nothing for the champions to smile about on the long journey home.

Knocked out of the League Cup semi-final by Ross County on Sunday, they crashed to a second successive defeat here at Pittodrie and this one could not be blamed on quirky decisions or cruel twists of fate.

The truth is, Celtic’s players failed to turn up for the biggest match of the season so far and as soon as Aberdeen had realised it they simply stepped forward and claimed all three points with minimum fuss.

Yes, it took a howitzer from the outstanding Jonny Hayes – whose left hand was bandaged up after his comedy run-in with a neighbour’s pet pooch – to get them started.

But from the moment Hayes had lashed that one into the back of Craig Gordon’s net there was only ever going to be one winner of this top-of-the-table clash. When new boy Simon Church added a quick second before the half-time break it was all but over.

That Celtic failed to sink their teeth (sorry) into this contest either before or after that matchwinning double sums up Ronny Deila’s plight. His team lacks purpose and seems entirely unable to fight its way out of a corner.

Yes, Leigh Griffiths pulled one back in injury time but if ever there was a tale of too little, way too late then this was surely it.

That late scare aside, Aberdeen flattened Celtic for the second time this season without having a glove laid upon them. It’s the first time in 25 years they’ve beaten Celtic twice at home in the same league season.

They took that campaign to a last-day decider. After this result they have reason to believe they can do the same again. Or even go one better.

Second guessing Deila’s team selections can be a precarious business but there were at least two decisions that seemed obvious even by the Norwegian’s unpredictable standards.

Skipper Scott Brown was returned to the heart of Celtic’s engine room and Efe Ambrose taken out of harm’s way and escorted towards the bench.

And just like that the champions were made to look more sturdy than they had been last time out at Hampden when Ambrose brought the roof down on them with his latest clanger. Into his position stepped the surefooted Erik Sviatchenko. On paper Deila’s line-up looked the part.

But Derek McInnes had a plan to put this to the test and it involved throwing in new boy Church from the start at centre forward – a surprise move that saw Adam Rooney shunted to the right wing, with Hayes deployed in a more central area from where he could drop in and out of pockets of space like Aberdeen’s modern-day Artful Dodger.

With Niall McGinn running the left flank this was a team designed to attack Celtic’s defences from all angles.

Just as well then that Brown was back out there, all over Aberdeen’s frontmen like a rash from the first minute. In the space of 20 seconds he dumped McGinn then Hayes on to the seat of their pants and earned an early reintroduction to ref Steven McLean but from that moment on Brown fizzed around the midfield with a demonic intensity.

He set about his big comeback game like a man possessed, popping up almost anywhere and everywhere he was needed.

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After 15 minutes he even unloaded on Aberdeen’s goal with a venomous drive from distance that dipped just over. It was almost as if he was taking this game to the Dons all on his own.

In fact, it was exactly that. Because for all Brown was giving, there was a team-mate in green and white who was not fully at the races.

Nir Bitton was strolling around on the periphery of the battle while widemen Stuart Armstrong and Gary Mackay-Steven were offering little.

Griffiths was also struggling to get going even though he did send a deflected shot across the face of Scott Brown’s goal midway through the half.

For Aberdeen’s part, there was a great deal of energy and endeavour but Church was getting little change out of the impressive Sviatchenko and for all McGinn, Hayes and Rooney were attempting to join in, McInnes’s men were making no great progress.

Then suddenly everything changed 32 minutes in as first Church then Rooney went chasing after a long hopeful probe from the back.

The ball broke to Hayes who hit it on the half volley and sent a shot scorching through the icy night air from 25 yards. A startled Craig Gordon, who had hardly been troubled until now, hurled himself to his left but before he could get there the ball had exploded into the rigging behind him.

Gordon could scarcely believe what had just been done to him. But while Celtic were still in a state of self pity Aberdeen were busy hunting down a second goal.

And six minutes later they got it when Hayes drilled a delicious corner into the six-yard box, Kenny McLean got the run on Celtic’s defence to glance a header towards the net and Church stuck out a knee to bundle it over the line.

Where Celtic’s defenders were as all of this was going on remains a mystery. Deila had 15 minutes to find them during the half-time interval and remind them of their responsibilities. He also used that time to remove Armstrong and hand new boy Colin Kazim-Richards a second-half debut.

In his mounting desperation Deila resorted to a 4-4-2. That’s how serious things had become.

The Aberdeen players celebrate after taking a two-goal lead

The powerful Kazim-Richards added muscle and a point of focus to Celtic’s attack and almost pulled one back when he stretched to get on the end of a bobbling Griffiths cross only for the ball to evade his toe.

Still, at least Griffiths had some company up there at last. The trouble was Aberdeen were continuing to get forward in numbers down the other end, winning a succession of corners and forcing Gordon’s defence on to the back foot.

And with every attack or deadball delivery Celtic’s anxiety levels appeared to soar. McGinn tried his luck from fully 35 yards with a shot Gordon could have waved past his post. Instead the keeper was spooked into diving full length and turning it away for another corner.

Tempers were starting to fray too. Brown was lucky not to get into trouble for flicking out a boot at Hayes then Kazim-Richards had his name taken for leaving a boot in on Ash Taylor during another untidy exchange.

It was only in injury time that Griffiths wriggled clear to fire home from the edge of the area but the strike hardly raised a cheer from the travelling support who knew there was no way back.

Some of them may well feel the same about Deila who now heads to East Kilbride and the ultimate in no-win Scottish Cup ties.